I won't say it can't be heard but those resonances are up around 10 MHz. The amplifier output they show is NOT an audio amp. It's a better than average std def video amp. To reduce the effects an inline 'terminator', actually more along the idea of a grid stopper would damp out all the resonance as it would form a single pole low-pass filter with the cable capacitance as one of the components.

You NEVER drive a cable directly from the output of an opamp as the capacitance changes the stability. Check any operational amplifier data sheet for capacitive loading issues.

before you can sell a so called solution you must invent the problem 1st.

1) real audio amplifiers have a limited bandwidth and not able to support the rise / fall times to excite so called zip cord resonances.
2) most amplifiers feature damped series inductors to decouple their outputs from seeing the bad zip cord resonances which are shown well beyond the bandwidth of any audio signal, that they say is a the problem.
these are not a real world examples or problems

__________________
like four million tons of hydrogen exploding on the sun
like the whisper of the termites building castles in the dust

Ah, yet another peddler of expensive wire deliberatly misapplying basic engineering / physics in an attempt to blind the gullible. I don't think many of us need to stay awake nights worrying that our speaker wire is resonating a couple of decades or more above the HF limit of human hearing.

Are cable resonances real? Yes, just like any misterminated transmission line.

Can they be audible? No, unless your loudspeakers and ears extend up to MHz frequencies.

One small note: if a cable resonance happens to coincide with an interfering RF source then the effect of RF interference may be made worse. In this sense, and this sense alone, they may become audible. The solution is to improve the RF rejection of the equipment by adding filters on each port. Simple LC or RC low pass filter, adds a few pence to the cost.